FemtoFrameII-G_Manua..
Contents
1. Sample a Figure 5 FemtoFrame Il G opto mechanical layout 5 3 2 Alignment of the Optical Delav Make sure the iris diaphragm D1 is exactly at height 104 mm above the main breadboard of FemtoFrame and its optical center is exactiv above the grid Block the path of the beam Place the mirror M1 so that its geometric center is approximatelv at height 104 mm above the breadboard M1 should be orientated in such way that it reflects the probing beam towards M2 Unblock the beam and adjust M1 so that the beam strikes it approximatelv in its center Fix M1 Block the path of the beam Place the mirror M2 so that its geometric center is approximatelv at height 104 mm above the breadboard M2 should be orientated in such way that it reflects the beam towards the Retro Reflector Unblock the beam and with the kinematic holder of M1 make sure that the beam strikes M2 approximatelv at its geometric center Fix M2 Block the path of the beam Place the mirror M2 so that its geometric center is approximatelv at height 104 mm above the breadboard M2 should be orientated in such way that it reflects the beam towards M3 Unblock the beam and with the kinematic holder 14 IBPhotonics Ltd FemtoFrame Il G User s Guide of M2 make sure the beam strikes the Retro Reflector and after reflection strikes the geometric center of M3 Fix M32. 1 LASER SAFETV The FemtoFrame spectrometer is not a laser source itself However it works with laser sources classified under regulations established bv the Center for Devices and Radiological Health CDRH of the Food and Drug Administration as a Class IV laser products Precautions for working with Class IV High Power Lasers Follow strictly all safety precautions provided in the laser source manual e Wear laser protection eyewear at all times Eyewear must be appropriate for the generated wavelength and beam intensity If you are not sure what eyewear is appropriate consult your organization s Laser Safety Officer e Install the laser equipment in an enclosed and controlled access area Limit access to this area to trained users who are familiar with the principles and practices of laser safety e Post highly visible warning signs near the laser operation area such as the following LASER VS E AND OR INVISIBLE RADIATION VOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION POWER WAVELENGTHS AND PULSE WIDTH DEPEND ON PUMP OPTION AND LASER CONFIGURATION CLASS IV LASER PRODUCT e Maintain a brightly lit laser operation area This constricts the eye s pupil reducing the possibility of eye damage e Experiment setups should be above or below eye level for any standing or seated position in the laser operation area e Keep the protective cover on the laser at all times e Donotlook at the output beam even diffuse
3. 20 6 2 3 Configure Delay Line panel iii 22 6 2 4 Quick Measurement page ii 22 6 2 6 Measurement Page aa ai 25 6 2 7 Exit Page rics ELE 27 7 DAYSTO DAY OPERATION eer eee ee c ia E I RE SER PU ERE de ER tv a 28 7 1 Powering Up the Spectrometer iii 28 4 2 CED Camera setup uei ec tse cdi ette repe rep lest teen on ceste Pe aoa ree ere nette ERR 28 4 3 Optical Delay setup iii 28 7 4 ChopperSetup rone etin aa 29 7 5 Digital controller box setup enne eene nennen inertes eene 29 7 6 Probing beam alignment check LR 29 Fel P mp beam check p eiie tr reor tede eet Certe Eo eto a ei eiue b PEE ka iii 30 LIST OF FIGURES IBPhotonics Ltd FemtoFrame Il G User s Guide Figure 1 Various signal contributions to pump probe spectra 8 Figure 3 FemtoFrame Il G optical layout 10 Figure 4 Electrical block diagram of FemtoFrame II G 12 Figure 5 FemtoFrame Il G opto mechanical layout mnn nnnnnn anna 14 Figure 6 Page selectionitabs i ertet ara 19 Figure 7 Screenshot of the Alignment page nsara nsa 20 Figure 9 Quick Measurement page 24 Figure 11 Measurement Page ses 24 Figure 12 Typical color profile of white light generated in Sapphire ern 29 IBPhotonics Ltd FemtoFrame Il G User s Guide
4. Block the path of the beam Place the iris diaphragm D2 so that its geometric center is exactiv at height 104 mm above the main breadboard of FemtoFrame and its optical center is exactly above the grid Unblock the beam and using M3 make sure that the beam passes through D2 Using M3 and M4 repeat the adjustment operation until the beam passes through D2 at all positions of the Retro Reflector Fix D2 Block the path of the beam Place the beam splitter M5 so that its geometric center is approximatelv at height 104 mm above the breadboard Place the Photo Detector so that its geometric center is approximatelv at height 104 mm above the breadboard and fix it Unblock the beam and adjust M5 so that it reflects small part of the radiation in the Photo Detector The part of the beam that passes through M5 should pass through D2 also Fix M5 5 3 3 Alignment of the White Light Generator Block the path of the beam Place the filter F1 so that its geometric center is approximatelv at height 104 mm above the breadboard Unblock the beam and adjust F1 F1 should be orientated in such way that after passing through it the beam keeps its propagation direction it should pass through D2 also Fix F1 Block the path of the beam Place the Half Wave Plate HWP so that its geometric center is approximatelv at height 104 mm above the breadboard Unblock the beam and adjust HWP so that the beam passes through its geometric center HWP should be orientated i
5. Stop Run toggle switch used to switch between paused and active acquisition mode for CCD camera s e 15 Laser rep rate control used to input the rep rate of the laser e 16 Divider control used to input the divider rate e 17 SET button used to send the settings of the CCD e 18 Trigger mode ring menu used to select the type of triggering of the CCD available settings are Hardware and Software e 19 Offset control sets the offset of the CCD e 20 Sync Out indicator Indicates lack of triggering signal on CCD 21 IBPhotonics Ltd FemtoFrame Il G User s Guide 21 Save Spectrum used to ave the reference Spectrum of the white light as seen on the CCD 6 2 3 Configure Delav Line panel Included features are 1 Get acceleration button Used to retrieve the value for the acceleration time of translation stage 2 Get Speed button retrieves the current High Speed setting value 3 Set acceleration button Used to set the value for the acceleration time of translation stage 4 Set Speed button sets the High Speed setting value 5 Command Control Used to input a command for translation stage controller 6 Send button Used to send a command to translation stage controller 7 Response indicator displays the response of the translation stage controller 8 Exit Button used to close and exit the Configure Delay Line panel and return to main control utility 6 2 4 Quick Mea
6. cause interference with pumping amplifiers When aligning FemtoFrame take care that any reflection from the optical elements is not coming backward along the pump beam White light Pump requirements Energy per pulse gt 0 05 mJ Pulsewidth 20 200 fs Beam Diameter 4 10 mm near TEMoo Polarization Linear Repetition rate 0 1 5 kHz Wavelength 760 840 nm IBPhotonics Ltd FemtoFrame Il G User s Guide 3 BASICS OF OPERATION Femtosecond transient absorption spectroscopv is an extension of the traditional steady state absorption spectroscopy With this method the absorbance of a sample at a particular wavelength or range of wavelengths is measured as a function of time after excitation by a short pulse of light This technique utilizes two laser pulses pump and probe derived by the same pulsed laser source with adjustable time delay between them The sample is photoexcited pumped from the ground state to the excited state by a strong excitation pump pulse and is brought out of thermal equilibrium The excited state will decay to other states with a characteristic decay time By measuring the absorption of the weaker probe pulse which is delayed relative to the excitation pulse the time evolution of the state under study ground state excited state radical pair etc can be monitored This so called transient contains clues to both structural information and dynamics The contemporary advent of shorter puls
7. engineer 3 Block the input beams before opening the cover Make sure all optical components inside FemtoFrame are orientated according Fig 3 before unblocking the path of the beams Intense light beams their specular and scattered reflections can be emitted from various parts of FemtoFrame when the cover is opened 4 Maintain FemtoFrame and all connected experimental setups considerably bellow eye level to prevent accidental beam encounter Keep the beams enclosed where possible 5 Avoid viewing beams and specular reflections Use protective eyewear at all times when aligning and operating FemtoFrame Make sure that your protective glasses cover the tuning range of lasers used with FemtoFrame Remember that radiation generated through parametric processes can be beyond the range of human vision Remember that the protective glasses while protecting your eyes also prevent from seeing the beams Therefore be cautious even when using safety glasses 6 Observe all other safety precautions given in the user s manual IBPhotonics Ltd FemtoFrame Il G User s Guide The used power pulse energy inside FemtoFrame may vary upon the type of pump laser used The average input power mav exceed 100 mW with pulse duration ranging from 20 to 150 fs and hundreds of microjoules of pump energy Be very careful when aligning and working with FemtoFrame IBPhotonics Ltd FemtoFrame Il G User s Guide 2 PUMP REQUIREMENTS Good pe
8. external telescope before FemtoFrame is needed with larger pump beam size at FemtoFrame optical input It is important that the beam would not clip on anv aperture before FemtoFrame and inside of it in order to achieve good output results 5 2 CONNECTING THE DEVICES S Out Tigin Chopper Delay Line Composite PD In N Chop In Digital Freq Out Sync Out a Power Chopper Spectrograph LU PC Transl stage CCD USB Figure 4 Electrical block diagram of FemtoFrame Il G Take the Digital Box PC monitor and keyboard out of the delivery crate Place them near FemtoFrame at convenient locations Connect the lines of the translation stage chopper CCD camera photo diode and motor driver as illustrated on fig 4 Use only power supplies from IBPhotonics or contact our support team before connecting power supply from other manufacturer Start the PC and the original installed software and test whether the modules work according their specification If any component gives a malfunction please contact immediately the technical representative of IBPhotonics 12 IBPhotonics Ltd FemtoFrame Il G User s Guide 5 3 MOUNTING OF THE OF THE OPTICS Through this chapter please refer to the FemtoFrame lavout Figure 3 below FemtoFrame is delivered to the customers with the optics removed and packed separatelv for safetv issues Nevertheless
9. of the beams Place the Sample Holder construction so that its geometric center is above the grid of the breadboard Unblock the path and make sure the Sample Holder is in the focus of the SM1 mirror Fix the Sample Holder construction 5 3 5 Alignment of the excitation beam optics Block the path of the beam Place the Chopper adjacent to the M13 so it can chop the pumping beam Unblock the beam and make sure the excitation beam passes through the wheel of the Chopper Fix the Chopper Block the path of the beam Place the mirror M10 so that its geometric center is approximatelv at height 108 mm above the breadboard M10 should be orientated in such way that it reflects the beam towards M11 Unblock the beam and make sure the pumping beam strikes M10 at its center Fix M10 Block the path of the beam Place the mirror M11 so that its geometric center is approximatelv at height 108 mm above the breadboard M11 should be orientated in such way that it reflects the beam towards M9 as the beam propagates exactly above M8 and F4 Unblock the beam and using M10 make sure the pumping beam strikes M11 at its center Fix M11 Make sure the reflected from M11 beam strike M9 After reflection from M9 the pumping beam strikes SM1 and is reflected towards the Sample Using M11 make sure the pumping beam is focused in the Sample in the same spot as the white light continuum 5 3 6 Alignment of the beams towards the Monochromator Block the pat
10. parameters e 6 Sample Reference indicates the reference name of the current sample as set by the user e 7 Data File Indicator e 8 START button used to start the measurement When measurement is in progress button color changes to green and indication changes to Scanning e 9 STOP button used to stop the current measurement Upon pressing this button the software finalizes the current series on exposures may take some time and stops the data acquisition process e 10 Current Scan indicator shows the number of the current scan e 11 Current Delay indicator shows the current optical delay in picoseconds e 12 Done indicator turns on when measurement is finished e 10 SAVE AS button used to save data when measurement is finished 26 IBPhotonics Ltd FemtoFrame Il G User s Guide 6 2 7 Exit Page The tab on this page is used to uninitialize the hardware and to exit the program 27 IBPhotonics Ltd FemtoFrame Il G User s Guide 7 DAV TO DAV OPERATION 7 1 Powering Up the Spectrometer The evervdav power up routine is as described below For details please refer to the electrical connection diagram in appendix A 1 Za Switch on the digital controller box by the panel switch The red LED on the panel should switch on The controller powers up the CCD the translation stage and the photodiode module inside the main optical unit Switch on the optical chopper driver F
11. reflections are hazardous e While using the laser do not wear objects such as jewelry that may reflect or scatter the beam e Before working in front of the laser verify that the laser beam is off e Avoid blocking the output beam or its reflection with any part of your body e When possible create enclosures for beam paths and set up shields to prevent specular reflections IBPhotonics Ltd FemtoFrame Il G User s Guide e Set up an energy absorbing target to capture the laser beam preventing unnecessary reflections or scattering The FemtoFrame spectrometer operates with coherent radiation in visible and invisible to human eye infrared and ultraviolet spectral regions generated from Class IV laser products The greatest concern when using FemtoFrame is eye safety Direct reflected or scattered radiation present in FemtoFrame can cause permanent eye damage Apart from that the radiation present in FemtoFrame can also cause skin or clothing burn or ignite fire if hitting flammable substances Because of these reasons the user is advised to follow the measures listed below 1 This device and supplementary equipment must be located in a locked area with access to authorized personnel only This area must be marked by well defined warning signs and be off limits to everyone except authorization personnel 2 FemtoFrame must only be operated by qualified personnel who have been trained by IBPhotonics customer service
12. to the eddge Fix M6 Block the path of the continuum Place the filters dfl And Df2 so that their geometric centers Are exactly at height 104 mm above the main breadboard of FemtoFrame and its optical centers are exactly above the grid Unblock the path and using M5 and M6 make sure that the continuum passes through centrally through Df1 and df2 Block the path of the continuum Place the mirror M7 so that its geometric center is approximately at height 96 mm above the breadboard M7 should be orientated in such way that it reflects the continuum towards M9 Unblock the path and adjust M7 so that the continuum strikes its geometric center Fix M7 Block the path of the continuum Place the mirror M8 so that its geometric center is approximately at height 104 mm above the breadboard M8 should be orientated in such way that it reflects the continuum towards M9 probe beam Unblock the path and using M7 make sure the continuum strikes M8 Fix M8 Block the path of the probe and the reference beam Place the mirror M9 so that its geometric center is approximately at height 104 mm above the breadboard M7 should be orientated in such way that it reflects the beams towards SM1 Unblock the path and using F4 and M8 make sure the probe and reference beams are propagating parallel to each other and strike M9 The probe beam should be above the reference one Fix M9 16 IBPhotonics Ltd FemtoFrame Il G User s Guide Block the path
13. 740 760 780 800 820 Wavelength nm Figure 7 Screenshot of the Alignment page 20 IBPhotonics Ltd FemtoFrame Il G User s Guide e 1 CCD Intensity graph displays the signal s from the CCD sensors The signals are compensated with the user set value of the control Offset 15 e 3 Calibrate button used to open a spectral calibration panel e 4 Current pos ps indicator shows current position of the optical delay line in picoseconds e 5 Stop button used to stop the current motion of the optical delay line if in motion e 6 Set Zero button used to set the internal counter of the optical delay line to zero e 7 Destination ps control used to input the target delay in picoseconds e 8 Go button sends command to move the optical delay to the targeted position inputed in Destination ps control e 9 lt lt button sends command to move delay line towards negative delay to new position calculated as Current pos ps Step 10 Step ps control used to input the relative step for the motion of optical delay e 11 gt gt button sends command to move delay line towards positive delay to new position calculated as Current pos ps Step e 12 Home button used to send command to the optical delay line to move towards negative delay until arrives to the end limit position and stop there e 13 Configure button opens delay line translation stage configuration panel e 14
14. ctral evolution Local and inter chromophore transitions can be simultaneously detected and detailed information IBPhotonics Ltd FemtoFrame Il G User s Guide such as spectral intensities and shifts line shape and band width changes can be readilv detected and analyzed Induced excited state absorption ESA peaks are typical signals appearing in broadband pump probe spectra but besides these other contributions mav also be observed depending on the spectral range of interest such as stimulated emission from excited states and ground state bleaching Figure 1 Excited state absorption Ground state absorption Fluorescence AA A t A t 0 Stimulated emission Ground state Figure 1 Various signal contributions to pump probe spectra On the one hand the transient signals with varied spectroscopic origins might mix together complicate the spectra and add difficulties to the component assignments on the other hand however they offer more comprehensive spectral information and thus reveal more detailed dynamic processes In many instances stimulated emission signals assist the determination of species behavior providing complementary information to the spectral assignments solely by ESA analysis In many cases as shown in Figure 1 stimulated emission from excited states and ground state bleaching can be accounted for by examining corresponding steady state fluorescence and absorption data respec
15. e current series of exposures 16 Exposure time indicator shows the time to finish the series of exposures 18 Scan s indicator shows the measured rate of camera exposures 19 Filter toggle switch used to switch on and off the spectral filtering 20 Order control determines the order of the filter Values are in range 1 5 21 Sigma control determines the width of the window for bad data removal 22 From control determines the lower limit of the spectral interval for noise statistics 23 To control determines the upper limit of the spectral interval for noise statistics 24 Mean indicator shows the mean value of the amplitudes in the acquired spectrum 25 Standard Deviation indicator shows the standard deviation of the amplitudes in the acquired spectrum 23 IBPhotonics Ltd FemtoFrame Il G User s Guide Figure 9 Quick Measurement page Tr BPhotonics Femtorrame Control v24 File Edit Operate Tools Window Help l e ee i i Figure 11 Measurement Page 24 IBPhotonics Ltd FemtoFrame Il G User s Guide 6 2 6 Measurement Page Functionalitv of this page allows performing the actual measurement and monitoring the current status and signals from the current measurement The features on this page are e 1 TA Spectrum graph shows the last acquired pump probe spectrum e 2 Scan parameters clu
16. electric filter 20 DF2 800 nm Notch dielectric filter 21 M11 Mirror Al 2 concave 22 MB Mirror Ag dia 1 flat 23 MC Mirror Ag dia 1 flat 24 M13 Mirror AI dia 1 flat 25 Retro Retroreflector Ag dia51 mm 26 12 Lens fus f 500 mm 27 HWP2 Lambda 2 plate 400 800 nm 28 F2 Cuircular NVDF Filter dia 2 31 IBPhotonics Ltd FemtoFrame Il G User s Guide APPENDIX B List Of optimized parameter values FemtoFrame Il G S N 207 CCD Camera Model AS8216 Item Parameter Value Note No 1 Trigger Mode Hardware 2 Laser Rep rate 1000 3 Divider 16 4 Offset 4800 Translation stage Model Item Parameter Value Note No 1 Speed 2 Acceleration Chopper Model Thorlabs MC2000___ __S N_ ltem Parameter Value Note No 1 Wheel Type MC2F57 2 Divider D 2 3 Multiplier N 1 4 Frequency 62 Hz 1 Phase 0 2 trigger External 3 Sync out Target Controller S N 207 Item Parameter Value Note No 1 Divider 16 32 IBPhotonics Ltd FemtoFrame Il G User s Guide 33
17. es resulted in the capability to interrogate molecular motion with great detail Measurements over a broad spectral range are highly desirable as they allow for more accurate interpretation of data While single wavelength measurements can be achieved by using OPAs to tune both pump and probe wavelengths to cover the spectral range of interest the data collection time becomes enormous especially when long time scans with high signal to noise are required On the other hand using a broadband supercontinuum white light as a probe pulse allows detection of the sample absorption in a wide spectral range at one single exposure Furthermore fast data acquisition electronics combined with fast photodiode arrays or CCD detectors enables massive data transfer into the computer to take advantage of the increased information gathered in this technique in a far shorter experimental time To achieve this goal FemtoFrame pump probe spectrometers use a laser generated white light for probing This technique provides broad probing window spanning from the UV to the NIR spectral range The white light or super continuum method is highly advantageous over conventional single wavelength pump probe technique in its capability to capture and resolve reactant intermediate and product states simultaneously By measuring the pump probe spectra as a function of time one not only will obtain kinetic traces at multiple wavelengths but also will monitor the complex spe
18. ev should pass through the input slit of the Monochromator Fix F5 Block the path of the beams Place the filter F6 F6 should be positioned in such wav that only the lower of the beams the probe beam passes through it After passing through F6 the beam must keep its propagation direction it should pass through the input slit of the Monochromator Unblock the beam and fix F6 18 IBPhotonics Ltd FemtoFrame Il G User s Guide 6 SOFTWARE 6 1 Software Installation Minimum requirements for the FemtoFrame Il instrument control and data acquisition software and hardware are as following Desktop personal computer or notebook 2 0 GHz CPU clock rate or better 2GB RAM or more 160GB HDD volume or more Six USB2 0 ports FemtoFrame Il comes with the following software installation components NI Labview Runtime Engine package NIVISA Runtime package Driver and utility installation package for translation stage Driver and utility installation package for CCD camera Driver installation package for RS232 to USB adaptor cables Proper installation and configuration can be guaranteed only when the software is installed by an authorized service engineer For assistance please contact IBPhotonics technical support 6 2 Control Utility Description The panel of the FemtoFrame Control utility Figure 6 consists of four pages navigatable via four tabs on the top side Clicking on each tab switches to
19. everv single FemtoFrame spectrometer is previously tested and the mechanical components are positioned and orientated according Fig 3 Before starting to mount the optics in their positions please check whether the mechanical holders and components are correctly orientated 5 3 1 Alignment of the beams outside FemtoFrame W1 and W2 are the input windows of FemtoFrame for the probing and pumping beams accordinglv The output beam from the femtosecond amplifier should be separated bv a beamsplitter thus forming the probing and pumping beam The probing beam should enter FemtoFrame through the geometric center of W1 Use two iris diaphragms at height 137 mm and two mirrors in kinematic holders to properlv adjust and direct the probing beam into W1 The pumping beam should enter FemtoFrame through the geometric center of W2 Use two iris diaphragms at height 137 mm and two mirrors in kinematic holders to properlv adjust and direct the probing beam into W2 When aligning the beams outside FemtoFrame make sure thev are not clipped bv the used optics and diaphragms 13 IBPhotonics Ltd FemtoFrame Il G User s Guide Retro _ __ Reflector ma MS M3 ra UN E Sapp KI L DH 7 Df2 ON l M6 Ys Spectrograph Sh
20. generated in Sapphire 29 IBPhotonics Ltd FemtoFrame Il G User s Guide Observe the beam before the folding mirror M5 The WL beam should be propagate very close to the Sapp crystal without clipping Observe the spot in front of mirror M6 The WL should be centered on the Filter Df1 aperture Observe the beam before mirror M10 It should strike m10 close to the vertical edge without clipping Place the card in the sample holder The probe beam should propagate horizontally centered on the holder 5 6 mm above the holder front edge Observe the beams in front of L3 It should propagate via the M12 and filter F5 without clipping Beam should be exactly centered on the L3 aperture Observe the two beams in front of M13 Both beams should intersect each other approximatelv on the surface of M13 so the observable spot is only one It should hit M13 close to the side edge without clipping Switch on the FemtoFrame Control Utilitv click on Alignment page and toggle up the Run Stop button so the CCD camera start running Observe the WL spectra on the CCD graph If there is necessitv use small adjustments of the filter F1 iris D2 and lens L1 to optimize the spectrum shape and stabilitv If there is necessitv use filter F5 to optimize the WL amplitude in the CCD The peak intensitv should be around 50000 CCD units 7 7 Pump beam checkup For excitation beam alignment check the following procedure can be used a Using a whi
21. h of the beams after the Sample Place the mirror M12 so that its geometric center is approximatelv at height 106 mm above the breadboard M12 should be orientated in such way that it reflects the beams towards M13 and should be positioned so that after focusing from it the beams are focused in the input slit of the monochromator Unblock the path and make sure the probe and the pump beam strike M12 Fix M12 Block the path of the beams after the sample Place the beam blocker B in front of M12 adjacent to it At this position if the svstem is properlv aligned the pump beam should 17 IBPhotonics Ltd FemtoFrame Il G User s Guide be the lowest of the three beams The beam blocker must be positioned in such way that it stops the pump beam from anv further propagation towards the Monochromator Block the path of the beams after M12 Place the mirror M13 so that its geometric center is approximatelv at height 104 mm above the breadboard M13 should be orientated in such wav that it reflects the beams towards the input slit of the Monochromator Unblock the path and using M13 make sure the beams strike M13 Fix M13 Block the path of the beams Place the filter F5 so that its geometric center is approximatelv at height 104 mm above the breadboard Unblock the path and adjust F5 so that the beams pass through the filter F5 should be orientated in such way that after passing through it the beams keep their propagation direction th
22. h the sample both probe and reference are spectrally dispersed by a monochromator and simultaneously detected on CCD cameras The signals are collected in a two step measurement cvcle In each step probe and reference signals are recorded at certain conditions determined bv the state of the pump shutter or chopper The change in optical densitv is obtained using the standard formalism for pump probe spectroscopv IBPhotonics Ltd FemtoFrame Il G User s Guide OD log 12 7 where the lower index denotes the recorded probe pr signal The upper index characterizes the position of the optical chopper blade which controls the excitation beam exc pump chopper is open 0 pump chopper is closed The recorded signals at each step are result from integration typically for several 100 laser pulses The exact number of acquired laser shots within a single two step cycle is selectable and will depend on the specific experimental conditions The WLC probe pulse passes through several optical elements which introduce a chirp due to the group velocity dispersion GVD i e its different spectral components accumulate different group delays As a result different spectral components of the WLC pulse are interacting with the excited sample molecules at different delay times Before entering the sample the WLC spreads in time typically from several hundred fs up to ps depending on thickness and the refraction index dispersion of the
23. he panel divider control to select the ratio of division for the laser repetition rate Optimized ratio is given in Appendix B 7 6 Probing beam alignment check For probing beam alignment check the following procedure can be used a Using a white paper card and an IR viewer if necessary trace the laser beam that enters through the optical port W1 The beam should be centered on W1 and should strike the flat mirror M1 fig 5 without any clipping b Move the optical delay line to the minimum delay position and observe the beam reflected by mirrors M2 and M3 The beam should strike BS beamsplitter approximately on the center without any clipping c With IR viewer or in dark observe the beam reflected by BS It should hit the center of the photodiode module PD fig 5 d With IR viewer or in dark observe the beam transmitted though the programmable iris D2 It should be centered on the D2 aperture e Place the card on front of PM1 and observe the white light WL generated in the Sapp crystal The WL spot should be round and visibly stable in time When observed in dark the white light color typical profile should look approximately like the one shown on fig 12 The center part is white with yellowish greenish hue surrounded with narrow and greenish blue halo When pumped with enough energy a dark and wide red colored halo should be slightly visible outside the main spot Figure 12 Typical color profile of white light
24. lv IB Photonics Ltd 19A Plovdivsko Pole St Suite 2 Sofia 1756 Bulgaria Tel 359 887 330 322 FEMTO FRAME Il G Transient Absorption Spectrometer USER S GUIDE Rev A2 IBPhotonics Ltd FemtoFrame Il G User s Guide TABLE OF CONTENTS 1 LASER SAFETY ie 3 2 PUMP REQUIREMIN TS reiner eren eo ehe e enne REEF fa ere een dB serres eat se TE a anne tente dat e 6 3 BASICS OF OPERATION i iii paga tee ee etn ener nee eee dee ea sere aaa 7 4 SYSTEM OVERVIEW sciare aaa 9 5 INITIAL INSTALATION ere eene eret ee dote een o eate aeneo Re dr anie reden 12 5 1 POSITIONING AND CONNECTING OF FEMTOFRAME nennen enne anna nanna nennen 12 5 2 CONNECTING THE DEV CES eerte a de adea enne eiae eine t 12 5 3 MOUNTING OF THE OF THE OPTICS 13 5 3 1 Alignment of the beams outside FemtoFrame iii 13 5 3 2 Alignment of the Optical Delay eene eene nennen enne nnns 14 5 3 3 Alignment of the White Light Generator ss 15 5 3 4 Alignment of the optics of Sample ss 16 5 3 5 Alignment of the excitation beam optics 17 5 3 6 Alignment of the beams towards the Monochromator 17 6 SOFTWARE x Ad abib de ta et RR GR e e a Ee MU Dee p sa toda indi 19 6 1 Software Installati ri etre cete o nen rdc eee ove dicerem andas bed 19 6 2 Control Utility Description ii 19 6 2 1 Alignment Page aaa
25. n such wav that after passing through it the beam keeps its propagation direction it should pass through D2 also Fix HWP1 Block the path of the beam Place the Lens L1 so that its geometric center is approximatelv at height 104 mm above the breadboard Unblock the beam and adjust L1 so that the beam passes through its geometric center After passing through L1 the beam should be with circular cross section when observed with a white card Do not place the white card near the focus of L1 Fix L1 15 IBPhotonics Ltd FemtoFrame Il G User s Guide Block the path of the beam Place the Sapp crvstal Unblock the beam and adjust CaF2 so that the beam passes through it Fix the construction Block the path of the white light continuum after Sapp Place the M4 1 so that its geometric center is approximatelv at 104 mm height Unblock the path and observe with white card the reflected from M4 continuum It should be collimated after reflected from PM1 If not use the translation stage beneath m4 to relocate its position Repeat this procedure until you get collimated continuum after M4 5 3 4 Alignment of the optics of Sample Block the path of the continuum Place the mirror M6 so that its geometric center is approximatelv at height 104 mm above the breadboard M6 should be orientated in such way that it reflects the continuum towards m7 Unblock the path and adjust with the screws the continuum to strike m7 at very close
26. on mirror M5 is filtered by the filters DF1 and DF2 After reflection from the flat mirrors M7 M9 and M10 the continuum strikes the concave mirror M11 which focuses it in the sample cell The transmitted trough the sample probe beam is directed towards the lens L3 by the mirror M12 Beam passes trough variable neutral density filter F5 which serves to adjust the intensity of the probe light on the detector The focused by L3 probe light is supplied via the fiber cable to the grating spectrograph and CCD linear detector On the other hand the excitaion beam enters Femto Frame Il G through the optical port W2 After reflection from the flat mirrors M13 the pump passes through the blade of optical chopper CH focusing lens L2 and Neutral density filter F2 Further beam passes the half wave plate HWP2 and reference iris D4 and is directed toward the Sample by the mirror M14 11 IBPhotonics Ltd FemtoFrame Il G User s Guide 5 INITIAL INSTALATION 5 1 POSITIONING AND CONNECTING OF FEMTOFRAME Take the FemtoFrame box out of the deliverv crate and place on the optical table It is recommended to position the FemtoFrame along one side of optical table about 2 5 cm from the table edge Such positioning allows convenient access while operating or aligning the device Use the four clamps to attach FemtoFrame stable on standard 25 mm or 1 inch grid optical table FemtoFrame can accept the maximum beam size of 10 mm 1 e2 An additional
27. optical material on its way Independent measurements of the chirp of the WLC need to be carried out to correct the pump probe spectra for time zero differences Retro Reflector PD Figure 3 FemtoFrame II G optical layout 10 IBPhotonics Ltd FemtoFrame Il G User s Guide Femto Frame Il main optical unit is equipped with two optical input ports W1 and W2 fig 3 The laser beam 800nm that generates the probing light enters the box through the optical port W1 After reflection from the flat mirror M1 the beam strikes the Retro Reflector After the Retro Reflector the beam strikes the flat mirrors M2 and M3 and is directed towards the beam splitter BS BS reflects small part of the probing beam towards the photo diode PD for system synchronization The portion of the beam that passes through BS strikes the filter F1 which is used to adjust the power for the white light probe generation The half wave plate HWP is used to rotate the polarization of the beam to a user defined angle After F1 the beam passes thought the programmable iris D2 and is focused into the Sappfire Disc by the lens L1 The generated white light continuum is collimated by the concave mirror M4 and after a reflection
28. or more detail about the chopper power on sequence please refer to the chopper user s manual Power up and log in to the computer Navigate to the FemtoFrame control utility and double click to load CCD Camera setup For CCD camera setup the following procedure can be used a Set mode of triggering to by selecting from the drop down menu button and clicking SET Button The default value is Hardware Set Laser rep Rate by inputting the number in Hz and clicking SET button The default value is 1000 Hz Set Divider value by inputting the number in the field and clicking SET button The default value is 16 Set CCD offsets by inputting the values into the numeric slider The default value is 4800 Optical Delay setup Open the Optical delay Setup By clicking on the Configure button on Alignment page item 13 Retrieve the current values of the Speed And acceleration by clicking on the Get Speed and Get Acceleration buttons If needed set new values for Speed and acceleration of the translation stage by inputting the numerical values in the corresponding controls and clicking on the Get Speed and Get Acceleration buttons Exit the panel by clicking the Exit button 28 IBPhotonics Ltd FemtoFrame Il G User s Guide 7 4 Chopper setup Please refer to the chopper instruction manual for the procedure for setting the parameters Per optimized parameters are listed in Appendix B 7 5 Digital controller box setup Use t
29. rformance of FemtoFrame requires high pump qualitv in terms of both time and space coherence Therefore that ideal pump is diffraction limited laser beam with transform limited pulses and high pulse contrast Unlike with conventional lasers with coherent pump the phase modulation of pump pulse and or beam inevitably influences the output results To some extent performance of FemtoFrame is an indicator of qualitv of the pump laser radiation Spatial beam qualitv Non uniformitv of the beam reduces the energv conversion rate Presence of hot spots in the beam may ignite small scale self focusing that in turn leads to phase modulation Spatial temporal beam distortion In contrast to long pulse lasers astigmatism introduced bv improperlv aligned lenses of beam expanders reducers lead to distortion of temporal profile of the pulse across the beam This affects stronglv the qualitv of the white light continuum generated inside FemtoFrame and or the temporal resolution of the spectrometer Tilted pulses This phenomenon manifests itself in similar way as that discussed above However it originates from improper pulse compressor alignment Tilted pulses are produced when the angular dispersion is not completely cancelled The problem with this kind of distortion is that it can be easily overlooked using standard diagnostics equipment such as autocorrelator Feedback to pumping amplifier Reflections coming backward from FemtoFrame may
30. second interval If Lin Log 2 switch is set to position Log the value of this control represents the increment of the stepsize Enable interval 3 Start 3 ps Finish 3 ps and Lin Log 3 controls 25 IBPhotonics Ltd FemtoFrame Il G User s Guide These controls determine the enabling start and finishing points as well as the tvpe of scanning analogously to the corresponding controls for interval 2 see above text for details Enable interval 4 Start 4 ps Finish 4 ps and Lin Log 4 controls These controls determine the enabling start and finishing points as well as the type of scanning analogously to the corresponding controls for interval 2 see above text for details Enable interval 5 Start 5 ps Finish 5 ps and Lin Log 5 controls These controls determine the enabling start and finishing points as well as the type of scanning analogously to the corresponding controls for interval 2 see above text for details e 3 Size 1 Size 2 Size 3 Size 4 and Size 5 indicators these indicators show the number of delav points for the corresponding interval e 4 Load Parameters from Previous button used to load and set measurement scan parameters used in previous measurements Click to open a prompt for navigation and selection of a par file containing scan parameters saved in previous measurement 5 Expected finish Time indicator shows estimated finish time for a measurement with the inputted
31. ster shows information about the parameters of the current measurement Cluster contains the following controls No exposures control used to input number of exposures to accumulate and average in a single series Number of scans determines the number of scans of the optical delay line the data of which will be collected and averaged by the software Enable interval 1 Always ON this control is always switched on to ensure there is always at least one interval enabled for scanning Start 1 ps used to set the first start point of the first interval of delay times in picoseconds Finish 1 ps used to set the last finish point of the first interval of delay times in picoseconds Step1 ps the value of this control determines the size of the step in picoseconds for scanning in the first interval Enable interval 2 this control enables the use of second interval for delay times scanning Start 2 ps used to set the starting point of the second interval of delay times in picoseconds Finish 2 ps used to set the finish point of the second interval of delay times in picoseconds Lin Log 2 switch determines the type of scanning in interval 2 Lin corresponds to scanning with constant stepsize Log dermines scanning with continuously increasing stepsize Step1 ps If Lin Log 2 switch is set to position Lin this control determines the size of the step in picoseconds for scanning in the
32. surement page The features on this page are shown on figure 9 as follows 1 TA Spectrum graph shows acquired pump probe spectrum 2 Current pos ps indicator shows current position of the optical delay line in picoseconds 3 Stop button used to stop the current motion of the optical delay line if in motion 4 Set Zero button used to set the internal counter of the optical delav line to zero 5 Destination ps control used to input the target delay in picoseconds 6 Gol button sends command to move the optical delav to the targeted position inputed in Destination ps control 7 lt lt button sends command to move delay line towards negative delay to new position calculated as Current pos ps Step 8 Step ps control used to input the relative step for the motion of optical delay 22 IBPhotonics Ltd FemtoFrame Il G User s Guide 9 22 button sends command to move delay line towards positive delay to new position calculated as Current pos ps Step 11 Configure button opens delay line translation stage configuration panel 12 Stop Run toggle switch used to switch between paused and active acquisition mode for CCD camera s 13 Sync Out indicator shows lack of synchronization of the CCD from the laser 14 No Exposures control used to input number of exposures for a to accumulate and average in a series 15 Progress indicator stripe shows the progress in th
33. te paper card trace the pump beam that enters through the optical port W2 The beam should be centered on W2 and should strike the mirror M13 fig 5 without anv clipping Observe the excitation beam right after the iris diaphragm D4 The excitation beam should be centered on D4 aperture The WL beam should also be exactly centered on L2 and roughly centered on HWP2 and M14 Place the card inside the sample holder and observe the excitation and the probing beam spots Thev should visiblv overlap with each other 30 IBPhotonics Ltd FemtoFrame Il G User s Guide APPENDIX A List Of optical Components installed S N 207 For designators refer to fig 5 from the User s Guide Item Designat Description Note No or 1 MA Mirror HR 800nm dia 1 Flat 2 MB Mirror HR 800nm dia 1 Flat 3 MC Mirror HR 800nm dia 1 Flat 4 M1 Mirror HR 800nm dia 1 Flat 5 M2 Mirror HR 800nm dia 1 Flat 6 M3 Mirror HR 800nm dia 1 Flat 7 BS Beam splitter 4 1 Flat 8 HWp1 Lambda 2 plate 800 nm 9 F1 Linear NVDF filter 10 L1 Lens f 100 mm 11 Sapp Sapphire crystal 12 M4 Mirror Al dia 1 concave 13 M5 Mirror Al dia 1 flat 14 M6 Mirror Al dia 1 flat 15 M7 Mirror Al dia 1 flat 16 M9 Mirror Al dia 1 flat 17 M10 Mirror Al dia 1 flat 18 M12 Mirror Al dia 1 flat 19 DF1 800 nm Notch di
34. the corresponding page and the software in the corresponding mode of operation Figure 6 Page selection tabs 19 IBPhotonics Ltd FemtoFrame Il G User s Guide 1 Alignment Functions on this page allow optimization of the probe light bv monitoring of the signals coming from the CCD camera s adjustment of parameters of the CCD detectors control and parameter adjustment of the optical delav line This page also contains a panel for wavelength calibration 2 Quick Measurement Controls on this page allow optimization of the measurement bv monitoring of a transient absorption spectrum at a given optical delav User can also optimize the online filtering parameters 4 Measurement Functionalitv of this page allows for setting of the scan parameters inputting sample description information and performing the actual measurement and monitoring the current status and signals 5 Exit exit the program 6 2 1 Alignment Page The page function is to monitor the properties of the white light for both probe and reference beams and for alignment of the delav line The included features are shown in Figure 7 IBPhotonics FemtoFrame Control v 2 4 Ce Es File Edit Operate Tools Window Help FFRAM pie Alignment Quick Measurement Measurement Exit Optical Delay Current po 480 500 520 540 560 580 600 620 640 660 680 700 720
35. tively IBPhotonics Ltd FemtoFrame Il G User s Guide 4 SYSTEM OVERVIEW Figure 2 shows example arrangement of a femtosecond broadband pump probe experimental setup with FemtoFrame Il The laser source is a Titanium Sapphire based oscillator amplifier system that provides a pulse train of femtosecond pulses lt 200 fs with Ti Sapphire Amplifier Femto Frame ll Figure 2 Example arrangement of pump probe spectroscopv svstem millijoule energy at 800 nm and repetition rate of 0 1 5 kHz The output beam is be divided into several fractions bv beam splitters powering a second harmonic generator or an optical parametric amplifier for sample excitation while a smaller fraction of the laser output is used to generate the white light WL for broadband probing inside FemtoFrame Il This is achieved by tight focusing of the 800 nm or 400 nm laser pulses into a Sapphire or CaF monocrvstal plate Bv this means a usable probe sources that cover overlapping spectral regions in the UV VIS NIR spectral range from 250 to 900 nm are achieved In order to improve sensitivity of the measurement transient absorption spectrometer implements dual beam probe geometry and a software lock in technique The WLC is split into two beams probe and reference and focused into the sample using reflective optics The probe beam passes trough excited volume of the sample and the reference passes through the non excited spot After passing throug
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